27 research outputs found

    Quantitative patterns of vertical transmission of deformed wing virus in honey bees

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    <div><p>Deformed wing virus (DWV) is an important pathogen in a broad range of insects, including honey bees. Concordant with the spread of <i>Varroa</i>, DWV is present in the majority of honey bee colonies and can result in either low-level infections with asymptomatic bees that nonetheless exhibit increased colony loss under stress, or high-level infections with acute effects on bee health and viability. DWV can be transmitted vertically or horizontally and evidence suggests that horizontal transmission via <i>Varroa</i> is associated with acute symptomatic infections. Vertical transmission also occurs and is presumably important for the maintenance of DWV in honey bee populations. To further our understanding the vertical transmission of DWV through queens, we performed three experiments: we studied the quantitative effectiveness of vertical transmission, surveyed the prevalence of successful egg infection under commercial conditions, and distinguished among three possible mechanisms of transmission. We find that queen-infection level predicts the DWV titers in their eggs, although the transmission is not very efficient. Our quantitative assessment of DWV demonstrates that eggs in 1/3 of the colonies are infected with DWV and highly infected eggs are rare in newly-installed spring colonies. Additionally, our results indicate that DWV transmission occurs predominantly by virus adhering to the surface of eggs (transovum) rather than intracellularly. Our combined results suggest that the queens’ DWV vectoring capacity in practice is not as high as its theoretical potential. Thus, DWV transmission by honey bee queens is part of the DWV epidemic with relevant practical implications, which should be further studied.</p></div

    Weight Watching and the Effect of Landscape on Honeybee Colony Productivity: Investigating the Value of Colony Weight Monitoring for the Beekeeping Industry

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    <div><p>Over the last few decades, a gradual departure away from traditional agricultural practices has resulted in alterations to the composition of the countryside and landscapes across Europe. In the face of such changes, monitoring the development and productivity of honey bee colonies from different sites can give valuable insight on the influence of landscape on their productivity and might point towards future directions for modernized beekeeping practices. Using data on honeybee colony weights provided by electronic scales spread across Denmark, we investigated the effect of the immediate landscape on colony productivity. In order to extract meaningful information, data manipulation was necessary prior to analysis as a result of different management regimes or scales malfunction. Once this was carried out, we were able to show that colonies situated in landscapes composed of more than 50% urban areas were significantly more productive than colonies situated in those with more than 50% agricultural areas or those in mixed areas. As well as exploring some of the potential reasons for the observed differences, we discuss the value of weight monitoring of colonies on a large scale.</p></div

    Varroa-Virus Interaction in Collapsing Honey Bee Colonies

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    <div><p>Varroa mites and viruses are the currently the high-profile suspects in collapsing bee colonies. Therefore, seasonal variation in varroa load and viruses (Acute-Kashmir-Israeli complex (AKI) and Deformed Wing Virus (DWV)) were monitored in a year-long study. We investigated the viral titres in honey bees and varroa mites from 23 colonies (15 apiaries) under three treatment conditions: Organic acids (11 colonies), pyrethroid (9 colonies) and untreated (3 colonies). Approximately 200 bees were sampled every month from April 2011 to October 2011, and April 2012. The 200 bees were split to 10 subsamples of 20 bees and analysed separately, which allows us to determine the prevalence of virus-infected bees. The treatment efficacy was often low for both treatments. In colonies where varroa treatment reduced the mite load, colonies overwintered successfully, allowing the mites and viruses to be carried over with the bees into the next season. In general, AKI and DWV titres did not show any notable response to the treatment and steadily increased over the season from April to October. In the untreated control group, titres increased most dramatically. Viral copies were correlated to number of varroa mites. Most colonies that collapsed over the winter had significantly higher AKI and DWV titres in October compared to survivors. Only treated colonies survived the winter. We discuss our results in relation to the varroa-virus model developed by Stephen Martin.</p> </div

    (A-E) Venn diagrams showing the extent of overlap of the top-ranked 384 AIMs.

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    <p>(A-D) Overlap among the five selection methods (pairwise Weir & Cockerham’s F<sub>ST</sub>, F<sub>ST</sub>-based outlier test, Delta, I<sub>n</sub> and PCA) and the four training datasets (I, II, III and IV). (E) Overlap among the four training datasets, after averaging the information content obtained with the five selection methods, and (F) corresponding Spearman’s rank correlation coefficients.</p

    Primers used to establish the standard curve and qRT-PCR

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    <p>Primers used to establish the standard curve and qRT-PCR</p

    Relative expression (mean ± s.e.) of candidate genes important for apoptosis in <i>Nosema</i> infected honeybees.

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    <p><i>Nosema</i> sensitive (SN, solid circles) and tolerant (TN, solid squares) honeybees infected with 10<sup>5</sup><i>N</i>. <i>ceranae</i> spores, and their controls uninfected (SC, open circles and TC, open squares), were sampled at 1 day (green) and 6 days (blue) after inoculation. The genes JNK/<i>bsk</i> (Jun N–terminal kinase/ <i>basket</i>), <i>p53</i> (<i>tumor protein p53-like</i>), <i>iap–2</i> (<i>inhibitor of apoptosis protein 2;</i> predicted homologous gene to <i>Diap–1</i> in <i>D</i>. <i>melanogaster</i>), <i>casp–2</i> (<i>caspase–2–like; homologous gene to Dcp–1</i>), <i>casp–10</i> (<i>caspase–10–like; homologous gene to Dredd</i>) were predicted from <i>Drosophila melanogaster</i>. Sample sizes are ranging between six and ten pools of three individual honeybee midguts (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0140174#pone.0140174.s003" target="_blank">S3 Table</a>). Significance between treatment groups ***, <i>P</i> < 0.001.</p

    Varroa mite index (mites per 100 bees) from surviving and dead colonies.

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    <p>All surviving colonies (n = 16) were treated. Four colonies that died over the winter were treated. All untreated colonies died over winter.</p>#<p>n = 2 in October. Despite the treatment, mite infestation level increased, especially in the succumbing colonies. This could be due to ineffective treatment or subsequent mite reinvasion.</p>¤<p>Significant difference in mite index between surviving and dead colonies (* P<0.05, ** P<0.01, *** P<0.001).</p

    The Capaz scale before installation.

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    <p>The Capaz hivescale is an H-shaped platform made from aluminium and stainless steel, with the dimensions 420 x 480 x 86 mm (long x wide x high). Data are transmitted by cell phone. The rechargeable battery (12 V) lasts for 200 days. Ambient temperature and humidity are measured by default. Additional equipment is the rain collector and brood temperature sensor. Changes of the standard setup of the scale are done via the computer software. Photo: Capaz.</p

    Linear regression.

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    <p>(A-E) Plots between admixture proportions inferred from the initial 1183 SNP dataset and those inferred from the five AIMs panels (48-, 96-, 144-, 192-, 384-AIMs) using individuals of the holdout set. (F) Parameters and coefficients for each AIMs panel.</p
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